Method and apparatus for transmitting d2d discovery signal and communication system

ABSTRACT

Embodiments of the present disclosure provide a method and apparatus for transmitting a D2D discovery signal and a communication system. The method for transmitting includes: a UE selects a part of resources from a resource pool for transmitting a D2D discovery signal; the part of resources are selected in a manner of limiting number of times of transmission, or in a manner of limiting time interval, or in a manner of calculating a resource position; and transmits the D2D discovery signal by using the selected part of resources. With the embodiments of the present disclosure, malignant competitions may be avoided, resource utilization may be improved, and probabilities of undiscovery between UEs may be lowered; or detection may performed accurately, and complexity of a UE may be lowered.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of InternationalApplication PCT/CN2013/088770 filed on Dec. 6, 2013, the entire contentsof which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to the field of communications, and inparticular to a method and apparatus for transmitting a device-to-device(D2D) discovery signal and a communication system.

BACKGROUND

A D2D communication method refers to that data packets are communicatedby directly establishing a communication link between user equipments(UEs), such as a UE1 and a UE2, without needing via a core network, evenwithout needing via a base station. FIG. 1 is a schematic diagram of D2Dcommunications in the relevant art. As shown in FIG. 1, D2Dcommunications may be performed between UE1 and UE2 under coverage of abase station (eNB1). However, if under coverage of a base station,control signaling of the UE1 and UE2 will be sent by the base station.

Before D2D direct communications can be established between UEs, a D2Ddiscovery process, such as mutual discovery between the UE1 and the UE2,needs to be performed. For example, in order to achieve discovery of theUE1 by the UE2, the UE1 needs to transmit a D2D discovery signal, whichmay also be referred to as a beacon, in a time-frequency resource;

and the UE2 may discover the D2D discovery signal transmitted by the UE1by detecting the time-frequency resource. And quality of a channel fromthe UE1 to the UE2 may be known through signal detection.

It should be noted that the above description of the background ismerely provided for clear and complete explanation of the presentdisclosure and for easy understanding by those skilled in the art. Andit should not be understood that the above technical solution is knownto those skilled in the art as it is described in the background of thepresent disclosure.

SUMMARY

However, it was discovered by the inventors that according to aconclusion of a discussion of the current 3GPP, there exist thefollowing problems in an existing discovery mechanism: when a largenumber of UEs need to transmit D2D discovery signals at a time period,they need to acquire time-frequency resources through contention; andwhen a UE cannot determine whether the D2D discovery signal istransmitted successfully, in order to improve a rate of success oftransmission, the UE will frequently occupy a large number of resourcesthrough contention to transmit the D2D discovery signal, therebyresulting in malignant contention, and lowering resource utilization.

Furthermore, as simultaneous receiving and transmission in the sametime-frequency resource cannot be performed by a UE, it is prone thatsome UEs always cannot discover each other. For example, a UE1 and a UE2always transmit D2D discovery signals in the same time-frequencyresource, and they cannot discover each other. Furthermore, for a UE ata receiver end, the UE does not know a time-frequency resource where aUE it expects to discover transmits a D2D discovery signal. Hence, theUE at the receiver end will perform blind detection, thereby increasingcomplexity of the UE, and resulting in relatively large powerconsumption and insufficient power saving.

Embodiments of the present disclosure provide a method and apparatus fortransmitting a D2D discovery signal and a communication system.Resources are selected by limiting the number of times of transmissionor limiting a time interval, thereby avoiding malignant contention, andimproving resource utilization; and resources are selected bycalculating positions of the resources, thereby accurately performingdetection, and lowering complexity of the UE.

According to an aspect of the embodiments of the present disclosure,there is provided a method for transmitting a D2D discovery signal,including:

selecting a part of resources by a UE from a resource pool fortransmitting a D2D discovery signal; wherein, the part of resourcesis/are selected in a manner of limiting number of times of transmission,or in a manner of limiting time interval, or in a manner of calculatinga resource position; and

transmitting the D2D discovery signal by using the selected part ofresources.

According to another aspect of the embodiments of the presentdisclosure, there is provided an apparatus for transmitting a D2Ddiscovery signal, including:

a resource selecting unit configured to select a part of resources froma resource pool for transmitting a D2D discovery signal; wherein, thepart of resources is/are selected in a manner of limiting number oftimes of transmission, or in a manner of limiting time interval, or in amanner of calculating a resource position; and

a signal transmitting unit configured to transmit the D2D discoverysignal by using the selected part of resources.

According to a further aspect of the embodiments of the presentdisclosure, there is provided a communication system, including:

a first UE configured to select a part of resources from a resource poolfor transmitting a D2D discovery signal; wherein, the part of resourcesis/are selected in a manner of limiting number of times of transmission,or in a manner of limiting time interval, or in a manner of calculatinga resource position; and transmit the D2D discovery signal by using theselected part of resources; and

a second UE configured to perform blind detection according to theresource pool for transmitting the D2D discovery signal to receive theD2D discovery signal, or configured to receive the D2D discovery signalin a selected resource in a manner of calculating a resource position.

According to still another aspect of the embodiments of the presentdisclosure, there is provided a computer-readable program, wherein whenthe program is executed in a UE, the program enables the UE to carry outthe method for transmitting a D2D discovery signal as described above.

According to still another aspect of the embodiments of the presentdisclosure, there is provided a storage medium in which acomputer-readable program is stored, wherein the computer-readableprogram enables a UE to carry out the method for transmitting a D2Ddiscovery signal as described above.

An advantage of the embodiments of the present disclosure exists in thatresources for transmitting a D2D discovery signal are selected bylimiting the number of times of transmission or limiting a timeinterval, thereby avoiding malignant contention, improving resourceutilization, and lowering a probability of non-discovery between theUEs; and resources for transmitting a D2D discovery signal are selectedby calculating positions of the resources, thereby accurately performingdetection, and lowering complexity of the UE.

With reference to the following description and drawings, the particularembodiments of the present disclosure are disclosed in detail, and theprinciple of the present disclosure and the manners of use areindicated. It should be understood that the scope of the embodiments ofthe present disclosure is not limited thereto. The embodiments of thepresent disclosure contain many alternations, modifications andequivalents within the scope of the terms of the appended claims.

Features that are described and/or illustrated with respect to oneembodiment may be used in the same way or in a similar way in one ormore other embodiments and/or in combination with or instead of thefeatures of the other embodiments.

It should be emphasized that the term “comprise/include” when used inthis specification is taken to specify the presence of stated features,integers, steps or components but does not preclude the presence oraddition of one or more other features, integers, steps, components orgroups thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the disclosure can be better understood with referenceto the following drawings. The components in the drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present disclosure. To facilitateillustrating and describing some parts of the disclosure, correspondingportions of the drawings may be exaggerated in size.

Elements and features depicted in one drawing or embodiment of thedisclosure may be combined with elements and features depicted in one ormore additional drawings or embodiments. Moreover, in the drawings, likereference numerals designate corresponding parts throughout the severalviews and may be used to designate like or similar parts in more thanone embodiments.

FIG. 1 is a schematic diagram of D2D communications in the relevant art;

FIG. 2 is a flowchart of the method for transmitting a D2D discoverysignal of an embodiment of the present disclosure;

FIG. 3 is a schematic diagram of a resource pool of an embodiment of thepresent disclosure;

FIG. 4 is another flowchart of the method for transmitting a D2Ddiscovery signal of the embodiment of the present disclosure;

FIG. 5 is a schematic diagram of a structure of the apparatus fortransmitting a D2D discovery signal of an embodiment of the presentdisclosure;

FIG. 6 is another schematic diagram of a structure of the apparatus fortransmitting a D2D discovery signal of the embodiment of the presentdisclosure;

FIG. 7 is a block diagram of a systematic structure of the UE of anembodiment of the present disclosure; and

FIG. 8 is a schematic diagram of a structure of the communication systemof an embodiment of the present disclosure.

DETAILED DESCRIPTION

These and further aspects and features of the present disclosure will beapparent with reference to the following description and attacheddrawings. In the description and drawings, particular embodiments of thedisclosure have been disclosed in detail as being indicative of some ofthe ways in which the principles of the disclosure may be employed, butit is understood that the disclosure is not limited correspondingly inscope. Rather, the disclosure includes all changes, modifications andequivalents coming within the terms of the appended claims.

Embodiment 1

An embodiment of the present disclosure provides a method fortransmitting a D2D discovery signal, which is described from a UE sideof a transmitter end performing D2D communications. FIG. 2 is aflowchart of the method for transmitting a D2D discovery signal of theembodiment of the present disclosure. As shown in FIG. 2, the methodincludes:

step 201: a UE selects a part of resources from a resource pool fortransmitting a D2D discovery signal; the part of resources is/areselected in a manner of limiting number of times of transmission, or ina manner of limiting time interval, or in a manner of calculating aresource position; and

step 202: the UE transmits the D2D discovery signal by using theselected part of resources.

In this embodiment, the resource pool for transmitting a D2D discoverysignal may be configured by configuration information transmitted by abase station when the UE is in coverage of the base station, and mayalso be configured in advance when there exists no coverage of the basestation, for example, the UE is configured in advance ex-works. However,the present disclosure is not limited thereto.

In this embodiment, the resource pool for transmitting a D2D discoverysignal may include one of time-domain, frequency-domain or code-domainresources, or a combination thereof. FIG. 3 is a schematic diagram ofthe resource pool of the embodiment of the present disclosure. As shownin FIG. 3, there are multiple subframe resources in a period T, and apart of the resources (such as a 2nd, a 4th, a 7th and a 9th subframes)may be resources available for transmitting a D2D discovery signal,which may form a resource pool for transmitting a D2D discovery signal.And the UE may select a part of the resources (such as the 2nd and the7th subframes) to transmit a D2D discovery signal.

It should be noted that FIG. 3 only schematically shows the resourcepool for transmitting a D2D discovery signal; however, the presentdisclosure is not limited thereto. The resource pool may be one of atime-domain resource, a frequency-domain resource and a code-domainresource, or a combination thereof, and a particular content of theresource pool may be determined according to an actual situation. A partof resources in the resource pool (such as one or more subframe(s)) maybe selected for transmitting a D2D discovery signal.

In this embodiment, the resource pool may be denoted by a bitmap. Alength of the bitmap may denote the period T, 1 in the bitmap may denoteavailable resources, and 0 in the bitmap may denote unavailableresources. The available resources denoted by the bitmap form theresource pool. The number of the available resources in the range of theperiod T can be seen from the bitmap, which may be denoted by m.

Alternatively, the resource pool may be denoted by parameters. Theparameters may include a period value and the number of the availableresources, or may include the period value, the number of the availableresources and position information on the available resources. Forexample, a parameter period T and the number m of the availableresources, may be configured for the UE, and particular positions of mavailable resources may be predefined, such as defining former msubframes in the range of the period T.

It should be noted that expression manners of the resource pool areschematically described above only; however, the present disclosure isnot limited thereto. The present disclosure shall be further describedbelow taking that the UE is covered by the base station as an example.

FIG. 4 is another flowchart of the method for transmitting a D2Ddiscovery signal of the embodiment of the present disclosure. As shownin FIG. 4, the method includes:

step 401: a UE receives configuration information on the resource pooltransmitted by a base station.

In this embodiment, the resource pool may be configured by an operationadministration and maintenance (OAM) entity for one or more basestation(s).

Multiple base stations may be configured with the same resource pool, ormultiple base stations may be configured different resource pools havingoverlapped resources; for example, positions of resources betweenneighboring base stations are ensured that there are overlapped parts;or multiple base stations may be configured different resource poolshaving no overlapped resources; for example, positions of resourcesbetween neighboring base stations are not overlapped.

In this embodiment, the base station may notify the configurationinformation of the resource pool to the UE in a broadcast or unicastmanner; furthermore, the UE may receive an auxiliary parameter forselecting the part of resources transmitted by the base station; forexample, besides the position information on the resource pool, otherparameters may be contained, such as a maximum number of times oftransmitting D2D discovery signals by the UE permitted in a time period,which may be denoted by n, or a minimum time interval between two timesof transmitting D2D discovery signals, which may be denoted by t1.

Step 402: the UE selects a part of resources from the resource pool fortransmitting a D2D discovery signal; the part of resources is/areselected in a manner of limiting number of times of transmission, or ina manner of limiting time interval, or in a manner of calculating aresource position.

In an implementation, a random selection manner may be used; and the UErandomly selects one or more subframe(s) from the resource pool (such asavailable subframe resources) for transmitting a D2D discovery signal.

In another implementation, the manner of limiting number of times may beused; in a case where the UE is covered by the base station, a networkside may configure the UE with a limited number of times; for example, amaximum number of times of transmission of the UE in a time period (suchas a cycle) is n; and in a case where the UE is not covered by the basestation, the parameters may be predefined, and the UE may selectresources in a period to transmit D2D discovery signals for at most ntimes according to the parameters.

In a further implementation, the manner of limiting time interval may beused; in a case where the UE is covered by the base station, the networkside may configure the UE with a maximum time interval between two timesof transmitting D2D discovery signals; for example, a maximum timeinterval between two successive times of transmitting D2D discoverysignals is t1; and in a case where the UE is not covered by the basestation, the parameters may be predefined, and the UE may selectresources for transmitting a D2D discovery signal according to theparameters, so as to avoid that the time interval between two times oftransmitting D2D discovery signals is less than t1.

In still another implementation, the manner of calculating a resourceposition may be used, which may include: determining one or moresubframe position(s) by using ID of the UE, and determining positions ofradio frames, so as to determine a part of resources in the resourcepool.

Taking the manner of parameters of the resource pool as an example, theUE may learn parameters related to the resource pool which areconfigured based on the base station or preconfigured, including theperiod T and the number of available subframe resources in the range ofthe period T, the number being denoted by m.

In this implementation, the ID of the UE, UE_ID, may be ID uniquelyidentifying the UE; for example, it may be a cell radio networktemporary identifier (C-RNTI), or proximity service (ProSe) UE_ID, orphysical layer cell identity (PCI), or an evolved cell global identifier(ECGI); however, the present disclosure is not limited thereto, andother UE_ID may also be employed.

Furthermore, before being used, the UE_ID may be preliminarilyprocessed; for example, UE_ID=UE_ID original mod 1024, that is, modulooperation is performed on original ID; and this scheme may be applied toselection of time-domain resources.

In this implementation, the method for determining one or more subframeposition(s) by using the UE_ID may be as expressed in Table 1:

TABLE 1  (1) selecting a q₀-th subframe from m available subframes;where, m is the number of subframes in the resource pool, and q₀ isdetermined by using the formula below:  UE_ID = m * p₀ + q₀, 0 ≦ q₀ < m;where, UE_ID is the ID of the UE, and p₀ and q₀ are positive integers;(2) selecting a (1+q₁)-th subframe in the m available subframes;  where,p₀ = m * p₁ + q₁, 0 ≦ q₁ < m; and if 1+ q₁=m, a 0-th subframe will beselected;  ...... (i) selecting a (1+q_(i−1))-th subframe in the mavailable subframes;  where, p_(i−2) = m * p_(i−1) + q_(i−1), 0 ≦q_(i−1) < m; and 2 ≦ i ≦  imax, m^((imax−1)) ≦ UE_ID ≦ m^(( imax)),p_(i−1), q_(i−1) and i being positive integers; and if 1+ q_(i−1)=m, a0-th subframe will be selected.

Following description shall be given by way of examples. Assuming thatUE_ID=100, m=64, then p₀=1, q₀=36; a 36th subframe in the m availablesubframes may be selected for transmitting D2D discovery signals. It canbe determined from UE_ID=100, m=64 that imax=2, thereby determiningp₁=0, q₁=1; and furthermore, a 2nd subframe in the m available subframesmay be selected for transmitting D2D discovery signals.

Assuming that UE_ID=100, m=8, then p₀=12, q₀=4; a 4th subframe in the mavailable subframes may be selected for transmitting D2D discoverysignals. It can be determined from UE_ID=100, m=8 that imax=3, therebydetermining p₁=1, q₁=4; and furthermore, a 5th subframe in the mavailable subframes may be selected for transmitting D2D discoverysignals. And it may be determined that p₂=0, q₂=1, and a 2nd subframe inthe m available subframes may be selected for transmitting D2D discoverysignals.

In this implementation, determination of positions of the radio framesmay be as follows: determining a first position of a time-domainresource for transmitting a D2D discovery signal as a system framenumber (SFN), which is 0, and a subframe number is also 0. For theperiod T (less than 10240 ms), its unit might be assumed as millisecond(ms), and a starting point of a time-domain position of the resource fortransmitting a D2D discovery signal satisfies (SFN*10 mod T)=0. However,the present disclosure is not limited thereto. For example, thepositions of the radio frames may also be determined by using othermethods.

In this implementation, imax time-domain resource positions may betotally obtained. If the UE is permitted to transmit a D2D discoverysignal once in each period, the UE transmits D2D discovery signals oncerespectively in imax periods. And if the UE is permitted to transmitmultiple D2D discovery signals in each period, the UE may occupy imaxtime-domain positions obtained by using the method shown in Table 1 in aperiod to transmit D2D discovery signals.

Step 403: the UE transmits the D2D discovery signal by using theselected part of resources.

In this embodiment, at the receiver end, the UE may perform blinkdetection according to the resources configured by the base station orpreconfigured resources. Alternatively, if the transmitter end transmitsD2D discovery signals in the manner of calculating a resource position,the UE of the receiver end may learn a particular position of the UE fortransmitting the D2D discovery signals according to the configuredparameters and the method shown in Table 1, and may receive the D2Ddiscovery signals at accurate time-domain positions.

It can be seen from the embodiment that the resources are selected bylimiting the number of times of transmission or limiting a timeinterval, thereby avoiding malignant contention of resources, improvingresource utilization, and lowering a probability of non-discoverybetween the UEs; and resources are selected by calculating positions ofthe resources, thereby accurately performing detection, and loweringcomplexity of the UE.

Embodiment 2

An embodiment of the present disclosure provides an apparatus fortransmitting a D2D discovery signal, which may be configured in a UE.This embodiment corresponds to the method for transmitting a D2Ddiscovery signal described in Embodiment 1, with identical contentsbeing not going to be described herein any further.

FIG. 5 is a schematic diagram of a structure of the apparatus fortransmitting a D2D discovery signal of the embodiment of the presentdisclosure. As shown in FIG. 5, the apparatus 500 for transmitting a D2Ddiscovery signal includes: a resource selecting unit 501 and a signaltransmitting unit 502.

The resource selecting unit 501 is configured to select a part ofresources from a resource pool for transmitting a D2D discovery signal;the part of resources is/are selected in a manner of limiting number oftimes of transmission, or in a manner of limiting time interval, or in amanner of calculating a resource position; and the signal transmittingunit 502 is configured to transmit the D2D discovery signal by using theselected part of resources.

As shown in FIG. 5, the apparatus 500 for transmitting a D2D discoverysignal may further include: a configuration receiving unit 503configured to receive configuration information of the resource pooltransmitted by a base station. Furthermore, the configuration receivingunit 503 may be configured to receive an auxiliary parameter forselecting the part of resources transmitted by the base station.

In this embodiment, the resource pool may be denoted by a bitmap, or mayalso be denoted by a parameter; however, the present disclosure is notlimited thereto.

In this embodiment, the part of resources may be selected from theresource pool in a random manner, or the part of resources may beselected from the resource pool by limiting the number of times oftransmission, or the part of resources may be selected from the resourcepool by limiting a time interval. Furthermore, the part of resources maybe selected from the resource pool by calculating positions of theresources.

FIG. 6 is another schematic diagram of a structure of the apparatus fortransmitting a D2D discovery signal of the embodiment of the presentdisclosure, in which the apparatus for transmitting in using the mannerof calculating positions of the resources is shown. As shown in FIG. 6,the apparatus 600 for transmitting a D2D discovery signal includes: aresource selecting unit 501, a signal transmitting unit 502 and aconfiguration receiving unit 503.

The resource selecting unit 501 may further include a subframedetermining unit 601 and a radio frame determining unit 602. Thesubframe determining unit 601 is configured to determine one or moresubframe position(s) by using ID of the UE; and the radio framedetermining unit 602 is configured to determine a position of a radioframe, so as to determine the part of resources in the resource pool.

In this embodiment, the apparatus for transmitting a D2D discoverysignal may be configured in a UE.

FIG. 7 is a block diagram of a systematic structure of the UE of anembodiment of the present disclosure. As shown in FIG. 7, the UE 700 mayinclude a central processing unit (CPU) 100 and a memory 140, the memory140 being coupled to the central processing unit 100. It should be notedthat this figure is illustrative only, and other types of structures mayalso be used, so as to supplement or replace this structure and achievetelecommunications function or other functions.

In an implementation, functions of the apparatus 500 or 600 fortransmitting a D2D discovery signal may be integrated into the centralprocessing unit 100. The central processing unit 100 may be configuredto: select a part of resources from a resource pool for transmitting aD2D discovery signal; the part of resources is/are selected in a mannerof limiting number of times of transmission, or in a manner of limitingtime interval, or in a manner of calculating a resource position; andtransmit the D2D discovery signal by using the selected part ofresources.

In an implementation, the apparatus 500 or 600 for transmitting a D2Ddiscovery signal and the central processing unit 100 may be configuredseparately. For example, the apparatus 500 or 600 for transmitting a D2Ddiscovery signal may be configured as a chip connected to the centralprocessing unit 100, with its functions being realized under control ofthe central processing unit 100.

As shown in FIG. 7, the UE 700 may further include a communicationmodule 110, an input unit 120, an audio processor 130, a camera 150, adisplay 160, and a power supply 170. Functions of the above componentsare similar to those in the relevant art, which shall not describedherein any further. It should be noted that the UE 700 does notnecessarily include all the parts shown in FIG. 7, and the abovecomponents are not necessary; and furthermore, the UE 700 may includeparts not shown in FIG. 7, and the relevant art may be referred to.

It can be seen from the embodiment that the resources are selected bylimiting the number of times of transmission or limiting a timeinterval, thereby avoiding malignant contention of resources, improvingresource utilization, and lowering a probability of non-discoverybetween the UEs; and resources are selected by calculating positions ofthe resources, thereby accurately performing detection, and loweringcomplexity of the UE.

Embodiment 3

An embodiment of the present disclosure provides a communication system,including the UE described in Embodiment 2.

FIG. 8 is a schematic diagram of a structure of the communication systemof the embodiment of the present disclosure. As shown in FIG. 8, thecommunication system 800 includes a base station 801, a first UE 802 anda second UE 803. The first UE 802 may be the UE 700 described inEmbodiment 2.

The first UE 802 is configured to select a part of resources from aresource pool for transmitting a D2D discovery signal; the part ofresources is/are selected in a manner of limiting number of times oftransmission, or in a manner of limiting time interval, or in a mannerof calculating a resource position; and transmit the D2D discoverysignal by using the selected part of resources;

and the second UE 803 is configured to perform blind detection accordingto the resource pool for transmitting the D2D discovery signal toreceive the D2D discovery signal, or configured to receive the D2Ddiscovery signal in a selected resource in a manner of calculating aresource position.

It should be noted that FIG. 8 shows a case where the first UE 802 andthe second UE 803 are under coverage of the base station. However, thepresent disclosure is not limited thereto, and the first UE 802 and thesecond UE 803 may also not be covered the base station. Furthermore, thefirst UE 802 and the second UE 803 may be covered by different basestations, and a particular scenario may be determined according to anactual situation.

An embodiment of the present disclosure further provides acomputer-readable program, when the program is executed in a UE, theprogram enables the UE to carry out the method for transmitting a D2Ddiscovery signal as described in Embodiment 1.

An embodiment of the present disclosure provides a storage medium inwhich a computer-readable program is stored, the computer-readableprogram enables a UE to carry out the method for transmitting a D2Ddiscovery signal as described in Embodiment 1.

The above apparatuses and methods of the present disclosure may beimplemented by hardware, or by hardware in combination with software.The present disclosure relates to such a computer-readable program thatwhen the program is executed by a logic device, the logic device isenabled to carry out the apparatus or components as described above, orto carry out the methods or steps as described above. The presentdisclosure also relates to a storage medium for storing the aboveprogram, such as a hard disk, a floppy disk, a CD, a DVD, and a flashmemory, etc.

One or more functional blocks and/or one or more combinations of thefunctional blocks in Figures may be realized as a universal processor, adigital signal processor (DSP), an application-specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic devices, discrete gate or transistor logic devices,discrete hardware component or any appropriate combinations thereof. Andthey may also be realized as a combination of computing equipment, suchas a combination of a DSP and a microprocessor, multiple processors, oneor more microprocessors in communication combination with a DSP, or anyother such configuration.

The present disclosure is described above with reference to particularembodiments. However, it should be understood by those skilled in theart that such a description is illustrative only, and not intended tolimit the protection scope of the present disclosure. Various variantsand modifications may be made by those skilled in the art according tothe principles of the present disclosure, and such variants andmodifications fall within the scope of the present disclosure.

What is claimed is:
 1. A method for transmitting a D2D discovery signal,comprising: selecting, by a UE, a part of resources from a resource poolfor transmitting a D2D discovery signal; wherein, the part of resourcesis/are selected in a manner of limiting number of times of transmission,or in a manner of limiting time interval, or in a manner of calculatinga resource position; and transmitting the D2D discovery signal by usingthe selected part of resources.
 2. The method according to claim 1,wherein the method further comprises: receiving configurationinformation on the resource pool transmitted by a base station.
 3. Themethod according to claim 2, wherein the resource pool is configured forone or more base station(s) by an operation administration andmaintenance (OAM) entity.
 4. The method according to claim 3, whereinthe base stations are configured with identical resource pools, or thebase stations are configured with different resource pools havingoverlapped resources, or the base stations are configured with differentresource pools having no overlapped resource.
 5. The method according toclaim 1, wherein the resource pool is indicated by a bitmap.
 6. Themethod according to claim 5, wherein a length of the bitmap denotes aperiod, 1 in the bitmap denotes available resources, and 0 in the bitmapdenotes unavailable resources, the available resources denoted by thebitmap forming the resource pool.
 7. The method according to claim 1,wherein the resource pool is indicated by parameters.
 8. The methodaccording to claim 7, wherein the parameters comprise a period and anumber of available resources; or comprise the period, the number ofavailable resources and information on positions of the availableresources.
 9. The method according to claim 2, wherein the methodfurther comprises: receiving an auxiliary parameter for selecting thepart of resources transmitted by the base station.
 10. The methodaccording to claim 9, wherein in a case where the part of resourcesis/are selected in a manner of limiting number of times of transmission,the auxiliary parameter comprises: permitted number of times oftransmission by the UE in a period of time.
 11. The method according toclaim 9, wherein in a case where the part of resources is/are selectedin a manner of limiting time interval, the auxiliary parametercomprises: a minimum time interval between two times of transmission.12. The method according to claim 1, wherein in a case where the part ofresources is/are selected a manner of calculating a resource position,the method further comprises: determining one or more subframeposition(s) by using ID of the UE; and determining a position of a radioframe to determine the part of resources in the resource pool.
 13. Themethod according to claim 12, wherein the determining one or moresubframe position(s) by using ID of the UE comprises: selecting a q₀-thsubframe from m available subframes; where, m is the number of subframesin the resource pool, and q₀ is determined by using the formula:UE_ID=m*p₀+q₀, 0≦q₀<m, where, UE_ID is the ID of the UE, and p₀ and q₀are positive integers.
 14. The method according to claim 13, wherein thedetermining one or more subframe position(s) by using ID of the UEfurther comprises: selecting a (1+q_(i−1))-th subframe from m availablesubframes; where, p_(i−2)=m*p_(i−1)+q_(i−1), 0≦q_(i−1)<m, and 2≦i≦imax,m^((imax−1))≦UE_ID≦m^((imax)), p_(i−1), q_(i−1) and i are positiveintegers; and selecting a 0-th subframe from m available subframes if1+q_(i−1)=m.
 15. An apparatus for transmitting D2D discovery signal,comprising: a resource selecting unit configured to select a part ofresources from a resource pool for transmitting a D2D discovery signal;wherein, the part of resources is/are selected in a manner of limitingnumber of times of transmission, or in a manner of limiting timeinterval, or in a manner of calculating a resource position; and asignal transmitting unit configured to transmit the D2D discovery signalby using the selected part of resources.
 16. The apparatus according toclaim 15, wherein the apparatus further comprises: a configurationreceiving unit configured to receive configuration information of theresource pool transmitted by a base station.
 17. The apparatus accordingto claim 16, wherein the configuration receiving unit is furtherconfigured to receive an auxiliary parameter for selecting the part ofresources transmitted by the base station.
 18. The apparatus accordingto claim 15, wherein the resource pool is indicated by a bitmap, or theresource pool is indicated by parameters.
 19. The apparatus according toclaim 15, wherein the resource selecting unit further comprises: asubframe determining unit configured to determine one or more subframeposition(s) by using ID of the UE; and a radio frame determining unitconfigured to determine a position of a radio frame to determine thepart of resources in the resource pool.
 20. A communication system,comprising: a first UE configured to select a part of resources from aresource pool for transmitting a D2D discovery signal; wherein, the partof resources is/are selected in a manner of limiting number of times oftransmission, or in a manner of limiting time interval, or in a mannerof calculating a resource position; and transmit the D2D discoverysignal by using the selected part of resources; and a second UEconfigured to perform blind detection according to the resource pool fortransmitting the D2D discovery signal to receive the D2D discoverysignal, or configured to receive the D2D discovery signal in a selectedresource in a manner of calculating a resource position.